These are continuing studies to investigate how neural and local factors interact to regulate blood flow to human skeletal muscles. The investigators will explore the mechanisms of NO release by exploring the following specific aims: 1) Is NO-mediated forearm vasodilation observed during conlateral ischemic handgrip exercises after local anesthetic block of the satellite ganglion? 2) Is the forearm vasodilation seen during mental stress after stellate stress after stellate ganglion block NO-mediated and atropine sensitive? 3) is there evidence for vasodilation nerve traffic when mental stress is performed during systemic phenylephrine infusions that raise arterial pressure? 4) Can sympathoexcitatory maneuvers cause NO-dependent vasodilation in the leg? The proposed studies will help determine the mechanisms responsible for NO-mediated vasodilation during sympathoexcitatory maneuvers and explore their potential whole-body hemodynamic significance.